Trunk-line for telephone-exchanges.



Patented April 11, 1905.

UNTTED STATES PATENT OFFICE,

CHARLES I). SCRIBNICR. OF (I'IIOAGO, ANI) FRANK It. I\I(:BERI`Y, OF

DOWNIChS GROVE, ILLINOIS, ASSIGNOIIS TO 'Il'IIC IYICS'IICRI I ELICO- Tltl() COMPANY, OF CHICAGO, ILLINOIS, A (,ORPORA'IION OF ILLINOIS.

TRUNK-LINE FOR TELEPHONE-EXCHANGES.

SPECIFICATION forming' part of Letters Patent No. 787,120, dated April 1l, 1905.

Application filed April Z3, 1897. Serial No. 633,441.

Be it known that we` (ruanipns IC. ScninNrn-z, residing' at Chicago, in the county of (look, and Iii-:Axa l. \loBnn'rv, residing' at Downers (trove, in the county of l)upag'e, State of Illinois. citizens of the United States, have invented a certain new and useful Improvement a brief description of the mode of establishing` j and conducting' trunk connections between lines entering' different oflices of an exchange prior to the invention.

lt is common to provide signals in a teleplnsne-switchboard for the lines centering' in the switchboard andsuitable arrangements of circuits and sources of current to cause the operation of the signals as an incident to the use of the substationtelephones, the subscril ei"s act of taking' the telephone for use i serving to display a call-signal in the switchboard. It is further usual to associate with each plug' of a pair used in uniting lines thus equipped in the switchboard asignal which is controlled by the appliances at the station with whose line that plug is connected, so that through observation of the two signals referring' to the two plugs of a pair an operator is informed of the condition of the apparatus at both of the stations in communication. She

is thus enabled to transmit any necessary callsignals to either station and to effect disconnection of the lines immediately upon the return of both stationtelephones to their idle condition. These signals are commonly termed automaticsupm'visorysignals. The trunk-lines heretofore in use have not been adopted for uniting' lines furnished with such signals, inasmuch as they afforded no means for operatingl supervisory signals in uniformity with the, signals involved in local connections at both or all the ollices traversed by the complete connection.

'lhe present invention aims to provide means for bringing' the supervisory `ignal loefore the originating' operator who initiates the trunk connection under control of the substation connected with the distant terulinal of the trunk-line, and to provide a signal before the receiving'-operator, who completes the required connection to indicate to her also the condition of the apparatus at the called station, the intention being' to allow the originatincY operator to supervise the completed connection in a manner uniform with the supervision of local connections, but to permit the receiving' operator to call the required station one or more times, as may be necessary, in order that she may malte any special or distinctive call, if required.

To this end this invention consists in the combiiiation, with telephone-lines provided with means for determining llow of current in the lines in the use of the substationtelephones and a trunk-line for making connection with the calling' and with the called line, respectively, at its ditfcrent terminals, of a supervisory signal at the station of the originating operator and a supervisory signal at the station of the receiving operator, both of which signals are controlled from the called station.

ltconsists, further, in the combination," with such lines and the trunk-line, of two supervisory signals at the station of the originating' operator, with means for controllingl one of them from each ot' the united substations and a supervisory signal at the station of the receiving operator controlled from the called substation.

The invention also furnishes the usual signals for disconnection for the trunk-line, with suitable means for operating such signals independently of the supervisory signals.

The invention is illustrated in the attached drawing, wherein two telephone -lines are represented entering different offices of an exchange system and provided with signals of different types in the switchboards thereof, together with a trunk-line extending between the offices and supervisory and clearing-out signals associated with the trunk-line.

The line conductors 1 and 2 at station A are united through two bridges, the former of which is permanently closed and includes a polarized bell a and a condenser a', and the latter of which is normally open at a switch a2 and includes the receiving-telephone as and the transmitting-telephone at the station. The line conductors entering the central oice B traverse the windings of a signal-controlling relay L, after which they are led to the pole of a battery c and to earth, respectively. The line conductors are represented in the switchboard by normally open terminals of the spring-jack (l. The relay controls the circuit through a signal-lamp e, placed near the spring-jack Z in the switchboard. The local circuit comprises conductors 3 and 4, which lead to the poles of a localbatteryf. In the former of these conductors a resistancecoil g is interposed, while the latter includes the signal-lamp e. The conductors terminate in the normally separated contact-pieces of the relay. A branch 5 is led from the conductor 8 near its junction with the contact-piece of the relay to the thimble or ring contact d of the spring-jack for the purpose of permitting the relay to control a supervisory signal, which will presently be described. ln the switchboard the usual pai rs of connecting-plugs /L and /1/ are provided each with three contact-pieces for registering with the three parts of the spring-jacks (Z. Those contact-pieces of the two plugs which make connection with the linecontacts vof the spring-jack, the tip, and the short sleeve, respectively, are united by conductors 6 and 7, which constitute the plug-circuit. A condenser z' is interposed in each or these conductors. The usual calling-key /c is provided for disconnecting plug /a from its mate and connecting its line-contacts to the poles ofa generator of calling-current, which is not shown in the drawing. A listening-key Z is also furnished, by which the operator is enabled to connect her telephone m in a bridge of the plug-circuit. The sleeve-contact n of plug 7L, which makes connection with the thimble d ot' a spring-jack when the plug is inserted therein, forms the terminal of a wire 8, leading to the same pole of batteryf with which wire 4 is connected, and in this conductor a signal-lamp 0 is arranged, which is associated with the plug z in the switchboard. The contact-piece u of plug 7L forms the terminal of a similar wire 9, which includes the signal 0', associated with plug 7L. The connections of these local circuits are so arranged that when the plug 7i, for example, is inserted into the spring-jack d, the lamp e having' been lighted to signify a call, the supervisory lamp o is brought into parallel with lamp e and di-A verts sufficient current from it to bring about the darkening of both lamps. Thereafter the breaking of the circuit through lamp e by the return of the station-telephone to its switchhook at station A will permit the full current through resistance-coil to traverse the lamp o and will cause the illumination of that lamp as a signal to the operator.

The apparatus at station Al is substantially the same as that at station A; but it is equipped with a magneto-generator a5, which is adapted to operate an annunciator 7) in the switchboard at otiice C. The line conductors 1 and 2 ot' this line also are connected with the contact-pieces of aspring-jack (Z, which, however, is arranged to cut ofi' the annunciator when a plug is inserted into the spring-jack in the usual way.

A trunk-line 10 11 extends between the ot'- fices B and C. This line terminates at the ot'- iice B in a spring-jack p, adapted for use with the plug L, and at the otice C in a plug q, constructed for use with the spring-jacks (Z in that office. trunk-line, which is intended to be brought into connection with the shorter sleeve ot' plug L', a ground branch 12 is taken at office B. A relay fr is interposed in this ground branch, with a magnet of high impedance, together with a battery s or other source of current. This relay controls the continuity of a circuit 13 14, the former wire of which leads to the same poleJ of battery j with which wire 3 of the local signal-circuits is connected and includes a resistance-coil g' and the latter of which leads to the thimble ci of springjack p. A similar earth branch 15 is taken from wire 11 at station C, in which, likewise, a relay fr' and a source ot' current s' are interposed. This latter relay controls a local circuit including a source ot' current t, together with a signal-lamp u, which is controlled also by a plug-seat switch o in the seat or socket of plug q. This local circuit is made up of wires, 16 leading from one pole ot' the battery to one contact-piece ot' the relay, 17 from the other contact ot' the relay to one terminal of the lamp u, 18 from the other terminal of the lamp u to one contact-piece of the plugseat switch v, 19 completing the circuit from the other contact-piece of the plug-seat switch to the other terminal of the battery t. 1t is obvious that when the plug g is removed from its socket the break between wires 18 and 19 becomes closed, after which the lamp u will From the conductor 11 of this IOO IIO

be lighted as long as the relay r] is inert. The shorter spring (/'i of trunk-jack p (that which forms the terminal of conductor 10 of the trunk-line) is furnished with an anvil d, against which it is thrust when a plugI is inserted in the spring-jack. From this anvil il an earth branch 2O is led, which includes a source of current w together with an impedance-coil. To operate in conjunction with this source of current, a relay ,r is located in a ground branch 21 from conductor 10 at station U. 'lhis relay determines the continuity of a local circuit, which includes another signal-lamp M, associated with the plug' q, this circuit also being controlled by the plug-seat switch c. The local circuit is made up of wires, .)Q leading' from wire 16 to one contactpiece of the relay, 23 leading from the other contact-piece of the relay to one terminal of lamp u. and 21 extending` from the other terminal of the. lamp to wire 18, whence it finds circuit to battery f through the plug-seat switch and wire 1%). Lamp u will therefore also be lighted` when the plug' i] is removed from its seat while the relay ,1' is inert.

'lhe receiving operator at oiiice C is furnished with the usual calling-key for looping' a generator of calling-current into circuit with plug' q. She has also a telephone `m, which is connected by an or 1ler-circuit Q5 with the operators telephone m at station B, the continuity of the order-circuit being controlled by a key at the latter ofiice in the usual way.

in the normal condition of the apparatus the signals are all inert, the relays being in the positions shown in the drawings. The circuit through the line-lamp y is open at the switch -contacts of relay I). rPhe circuits through the supervisory lamps u and H/ are closed as respects the relays which control them, respectively, but are open at the plug'- seat switch w.

'lhe trunk-circuit is adapted for use in eX- tending connections from line Vfrom station A entering' oliice B as a calling-line to station A', connected with the ofiice C as a correspondent station. rl`he office B is termed the "originating" oliice, and the connection after its establishment is supervised at that station.

The oliice (.1 is termed the receiving ofiice, and the work done there is merely that of placing' the plug q in the spring-jack Z in compliance with an order sending' a call to the required station, and, tinally, removing the plug from the spring-jack to discontinue the connection. lt will be understood that other lines similar to that from station A terminate at the oflice B and that such lines may be united ordinarily by means of the plug's z/ 3 and their plug-circuits furnished the operator at that office. Similarly other stations A/ have lines leading into office C, where also local connections may be established by means of the usual appliances. (Not shown.)

5 The process of securing connection between stations A and Ay and the supervision of the completed connection is as follows: The receivingtelephone a is removed Yfrom its switch u2 at station A, whereby a closed path is provided at the station for current from battery c. The current produced in this path excites the relay which closes the local circuit 3 -L and lights the lamp c. The operator at ofiice B, answering the call, inserts plug /l/ into the spring-jack r/ and connects her telephone with the plug-circuit 6 T by means of listening-key l. The insertion of the plug in the spring-jack brings the supervisoryv lamp o into parallel with the line-lamp w, whereby a suliicient current is diverted from the linelamp to render it dark. The calling party at station A gives his order to the operator at ofiice B orally, 'following which the operator connects her telephone with the call-wire 25, leading to the operator at office C, wherein the line called for terminates, and instructs the operator there to connect a trunk-line with the line to station A. In pursuance of a well-known mode of operating the operator at oftice C, knowing what trunk-lines between oliice C and olice B are` idle, designates to the originating operator at ofiice B the trunkline which is to be employed. The originating operator then inserts plug /t' into spring'- liack p of that trunk-line, whereby the linecircuit 1 2 is extended through the plug-circuit T to the line conductors 10 11 of the trunk-line. The plug' and spring-jack together constitute what we term a connectionswitch, whereby one circuit may be united with the other. Simultaneously the receiving operator at ofiice (l inserts the terminal plug q of the same trunk-line into the springjack d of the called line, after which she depresses the ringing-key and thus transmits a signaling-current to ring the bell 1/ at station A'. 1n these different acts the follow'- ing changes are brought about in the local circuits associated with the plug-circuit 6 7 and the trunk-line 1011: The conductor t), through the supervisory lamp w, associated with the plug-circuit, becomes connected with conductors 14 and 13 to Yform a local circuit including the supervisory lamp and controlled by the switch-contacts of relay r. inasmuch asno current as yet exists through that relay, the conductor 7 being interrupted at the condenser ff and the conductor l1 being united to the open conductor 2 of line to station A@ this local circuit 9 l-t 13 is closed and the supervisory signal c is lighted. At the receiving ofiice C the removal ofthe plug q from its seat makes connection between wires 18 and 19, whereby a complete circuit is formed through supervisorylaim) fl, made up of wires 1G, 1T, 18, and 19, the relay fr being inert on account of th same circuit conditions before traced as affecting the relay 'f'. Hence the supervisory lamp a before the receivingoperator also is lighted. The insertion of plug' into spring-jack p IOO ITO

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forces the spring Z2 against its anvil Z3 and brings the conductor into a branch from line conductor 10 of the trunk-line. This change of circuit permits current to iow from battery w through wires 20, 10, and 21, which eX- cites the relay and effects the separation of its switch-contacts. Hence although the local circuit including the lamp fu is closed at the plug-seat switch o it is broken at the switch-contacts of relay n', and the lamp u remains dark. The condition of the signals immediately after the completion of the connection is then briefly: The line-lamp e of the calling-line is dark. The supervisory lamp 0 is dark, indicating to the supervising operator that the telephone at station A is in use. The supervisory lamp 0/ is lighted, signifying to the supervising operator that the telephone at the called station A is still on its switch. The supervisory lamp u before the receiving operator is lighted, signifying to that operator that the call transmitted to station A has not yet received attention. If the signal u should remain lighted for any unreasonable length of time, the receiving operator should transmit a second call. If the line to station A be a party-line or if it require any other specialized mode of calling, the operator at oflice C, who is accustomed to make connection with the line, may take any necessary steps in transmitting the call. When the subscriber at station A removes the receivingtelephone from its switch L2 in response to the call, the line-circuit 1 2 is completed through the conductor, including the telephones. A path is thus furnished for current from both batteries s and s into conductor 1l of the trunk-line, thence over line-wire 2, returning by line-wire 1, and finding circuit to earth through the relay Both relays fr and fr then become excited and attract their armatures, breaking the local circuits which they control. Thus the supervisory lamp o at ofce B and the supervisory lamp u. at oiiice C both become dark. Their extinction signifies to both the supervising and receiving operators that the called subscriber has answered. As long as the supervisory lamps remain in this condition the operators understand that the lines are in use. When at the termination of conversation the subscribers at stations A and A replace their telephones on the switches, the relays r, and r become inert. The relay b in breaking the circuit 3 4 diverts the full current of battery f through the resistance-coil g into the supervisory lamp 0, whereby that lamp becomes lighted. The relay fr in releasing its armature closes the circuit 9 14 13, causing the illumination of supervisory lamp o. The

simultaneous illumination of supervisory lamps o and o signifies to the supervising operator that the connection may be broken and is therefore followed by the removal of plugs L. and/z from 4the springjacks Z and p. The removal of plug la from trunk-jack p severs the connection of earth branch 20 with conductor 10 of the trunk-line, whereby the relay is deprived of current, the connection of batteries s and s' with the conductor lO through the medium of line-wires 1 and 2 having been previously broken. When this relay permits its lever to fall against its contact-anvil, current flows in the circuit through clearing-out lamp u', lighting that lamp. The simultaneous lighting of lamps u and u before the receiving operator is a call for disconnection of the trunk-line and is followed by the removal of the plug q from the springjack Z and the return of the plug' to its seat. Thus the supervising operator at the originating office is provided with a group of supervisory signals identical in arrangement and mode of operation with those which she uses in ordinary local connections, so that no special work is required on her part in supervising trunk connections. Likewise the receiving operator at ofiice C is furnished Ywith a signal which denotes to her the response of the called subscriber, whereby she is enabled to send any specialized signal that may be required in case the subscriber fails to respond to the first call. She has also adistinct clearing-out signal calling for the removal of the trunk connection.

W'e claim as the invention- 1. The combination with a calling and a called telephone-line and a trunk-line uniting them, of a continuously-operative source of current connected with the lines, a telephoneswitch at the substation of the called line, operated automatically in the use of the telephone apparatus thereat and controlling the flow of current in the line, and supervisory signal devices one at each terminal of the trunk-line, operated through the agency of `the current so controlled, whereby the condition of use or disuse of the substation telephone apparatus during connection is constantly indicated at both terminals of the trunk-line.

2. The combination with two telephonelines and means for producing current therein, each line having a telephone-switch at the substation thereof, operated automatically in the use of the substation telephone apparatus, controlling the flow of current in the corresponding line, of a trunk-line uniting said telephone-lines, two supervisory signal devices at one terminal of the trunk-line responsive to the telephone-switches at the respective substations, and a supervisory signal at the other terminal of the trunk-line responsive to the telephone-switch at the substation of the corresponding line.

3. The combination with two telephonelines, each provided with means for automatically determining the flow of current in the line in the use of the telephone, a trunk-line connected at one terminal with one of the lines, and a pair ot' plug's and the mug-circuit thereoic uniting' the other terminal ot the trunk-line with the other line, ot a supervisory signal t'or each plug' ot' the pair, and means lor controlling' one ot' said signals throug'h the ag'ency of current in each ot' the telephone-lines` and a supervisory sig'nal at the terminal ot the trunk-line distant from said plugs, said last-mentioned signal being' controlled by current in the line with which said terminal ot' the trunk-line is directly connected, as described.

-L The combination with two telephonelines, ot' a trunk-line uniting' the lines, a calling-key in the trunk-line at one terminal station thereot' adapted to transmit a call-signal to the station ot one ot' the lines, a supervisory signal at each terminal ot' the trunk-line, circuits including' the said signals together with sources ot current associated with the said truuk-line, and means t'or closing' the sig'- nal-eircuit to operate both ot` said signals in the use ot the telephone at the said called station; whereby both operators are int'ormed ot' the response to the call at a called station, as lescribed.

The combination with two subscribers tehmhone-lines, ot' a trunk-line lo ll, connec tion-switches at each terminal ot' the trunkline tor telephouically uniting' said subscribers lines through the trunk-line, an induction device. interposed in the circuit near one terminal ot' the truuk-line, a telephone-switch controlling the circuit at the substation ot the line which is connected to the other terminal ot' said trunk-line, branches l) l5 to a returnconductor from one trunk-wire l1l near the respective terminals thereof, a signal-controlling' magnet and a battery in each ot' said branches, the batteries being' opposed, a sig'- nal-controlling' magnet in a branch to said returi'i-couductor trom the other trunk-wire l() near one terminal, and a battery /f' applied to the said wire ll) at the other terminal in closing' the connection-switch thereat.

6. 'lhe combination with two telephonen lines, each having' meansat its station fordetermining' the iiow ot current in the line in the use ot' the telephone, and a trunk-line uniting' the lines, ot' three relays connected with the circuit to respond to current in the lines, a device adapted to transmit telephonie currents but to prevent the flow otl continuous currents interposed in the circuit between two otl the relays to bring' one ot' the relays under control ol` one ot' the substations and the other relays under the control ot' the other substation, and supervisorysignals controlled by the relays, the supervisory sig'nals which are controlled from the same station being' associated with opposite terminals ot' the trunk-line, as described.

T. 'lhe combination with two telephonelines, each provided with means at its substation t'or determining' the fiow ot' current in the line in the use ot' the telephone, said lines entering' ditlerent switchboards, a trunk-line between the switchboards having' one terminal directly connected with one ot the lines, and a pair otl plugs and a plug-circuit uniting' the other terminal otl thetruuk-line with the o ther telephone-line, ot' relays connected with the circuit, and supervisory signals associated with the connecti11g-plugs controlled by the said relays, a device interposed in the plugcircuit adapted to render the relays independently responsive to currents in the ditlerent telephone-lines, a calling-key in the trunl line circuit at the terminal thereof distant from the plug-circuit, a relay connected with the circuit near the same point, and a supervisory signal associated with the trunk-line controlled by the said last-mentioned relay, said relay being' responsive to current in the called line only, as described.

S. The combination with two telephonelines, each provided at its substation with a switch t'or closing` the line during' the use ot' the telephone, and a trunk-line uniting' the telephone-lines, ot' two relays connected with the circuit near one terminal olE the tru nit-line, supervisory sig'nals controlled by the relays, sources ot current adapted to produce current through the relays and lines when the linecircuits are closed at the substations, anda device in the circuit intermediate of the relays adapted to prevent current in either line from ati'ecting' the relay associated with the other line, a calling-key at the other terminal ot' the truuk-line, a relay connected with the circuit at the same terminal adapted to respond to current in the line with which said terminal is directly connected, and a supervisory signal controlled by that relay, substantially as described.

9. 'lhe combination with telcphone-lines provided at their subst-ations with means tor closing' the line-circuits during' the use, o'tl the telephones, a plug-circuit and a trunl -line uniting' the telephone-lines in complete circuit, ot'condensers in thc plug-circuit, a bridge ot' the circuit at each side ot' the condenser, and a relay and a source ot' current included therein, a supervisory signal associated with each plug' ot' the circuit controlled by the relay, a second bridge ot' the circuit at the distant terminal of the trunk-line, and a relay and a source ot' current therein, and a supervisory signal controlled by said second-mentioned relay, as described.

l0. The combination with two telephonelines, each provided at its substation with means tor determining` the tiow ot' current in the line in the use ot' the telephone, a plug'- circuit and a trunk-line uniting' the telephonelines in a complete circuit, a supervisory sig'- nal associated with each terminal plug' ot the plug-circuit, the ditlerent signals being' coutrolled by current in the ditlerent telephonelines, a supervisory signal at the other termi- IOO IOS

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nal of the trunk-line controlled by current in the line with which said terminal is directly connected, a clearing-out signal associated with said last-mentioned terminal ofthe trunkline, and a circuit changed in the act of making connection With the other terminal of the line determining the actuation of said clearing-out signal, substantially as described.

ll. The combination with a calling and a called line and a trunk-line uniting them, of means adapted to produce current in the lines, supervisory signal devices, one at each terminal of the trunk-line, a telephone-switch at the substation of the called line, operated automatically in the use of the telephone apparatus thereat, and controlling the HOW of CHARLES E. soRisNER.v FRANK R. MCBERTY.

Vitnesses:

ELLA EDLER, JAMES L. MCQUARRIE. 

